The larva of Hybocampa milhauseri—the Dragon of old Sepp—is highly remarkable. When young it has grand lateral horns in front, and a dorsal row; as it grows the lateral horns disappear. Dr. Chapman says[[267]] that he could not understand at first why any larva should have such remarkable angular outlines, curiously conspicuous corners and humps. But he afterwards found that the creature exactly resembled a curled oak leaf, eaten and abandoned by a Tortrix larva. This caterpillar also constructs an elaborate cocoon from which the moth escapes by an operation performed by the pupa, which is provided with two hard spines, called by Dr. Chapman sardine-openers. "By a lateral rotatory movement of the pupa, which obtains its fulcrum from the tightness with which it is grasped by the cocoon, it traverses over and over again" the same part of the cocoon till it is cut through; at the same time the spines act as guides to a fluid which is emitted so as to soften the part that has to be sundered.
Though many other larvae of Notodontidae are of most curious form and assume remarkable attitudes, yet this is not the case with all, and some are quite ordinary and like the caterpillars of common Noctuidae. This is the case with the species Rhegmatophila alpina we have selected to illustrate the metamorphosis of the Order (Fig. 157). Those who wish to form an idea of the variety of larval forms in this family will do well to refer to Packard's beautiful volume on the North American forms.[[268]] The family has a very wide distribution, but is absent from New Zealand and Polynesia, and appears to be but poorly represented in Australia. In Britain we have about two dozen species.
Fam. 12. Cymatophoridae.—A small family of nocturnal moths that connect the Bombyces with the Noctuids; they are usually associated with the latter, but are widely separated in Hampson's arrangement because of a slight difference of nervuration, nervule 5 being nearer to 6 than to 4, whereas in Noctuidae the reverse is the case. The Insects, however, in certain respects approach the Notodontidae, and are of interest if only as showing that the linear sequences we adopt in books are necessarily conventional, and to some extent deceptive. We have three genera in Britain; our pretty Peach-blossom, Thyatira batis, and the very different Buff-arches, T. derasa, being among them. Meyrick denies any connexion of this group with Noctuidae, and in his nomenclature Cymatophora becomes Polyploca, and the family, consequently, Polyplocidae.
Fam. 13. Sesiidae or Aegeriidae (Clear-wings).—A family of comparatively small extent; its members have frequently one or both pairs of wings in large part free from scales, the tip of the body tufted, the hind legs of one sex peculiar. The size is usually small, but in the largest forms the measurement may be but little less than two inches across the expanded wings. The pupa is of the kind classed as "incompletae" by Chapman, the appendages not being firmly glued to the body, and much mobility existing; an "eye-collar" is present, and the segments of the abdomen are armed with series of teeth. The larva is a concealed feeder, nearly naked and colourless, but with the legs normal in number—three thoracic, four abdominal pairs of feet, and the terminal claspers; these are sometimes but poorly developed; the larvae have a greater or less resemblance to those of Longicorn beetles, the habits of which they share. The family was formerly associated with the Sphingidae, with which it has no true relationship; it is more closely allied to the Tineidae. Some of the species have a certain resemblance to Hymenoptera, which is probably in most, if not in all cases merely incidental. The proper position of the family was pointed out by Butler,[[269]] but he did not distinguish it from Tinaegeriidae. Meyrick calls the family Aegeriadae, and places it in his series Tineina.
Fig. 193—Oedematopoda princeps. Africa. (After Walsingham.)
We have two genera of these Clear-wings in Britain. They are Trochilium (called variously Sesia, Sphecia, and Aegeria), with two species of comparatively large size, and Sesia (called variously Trochilium and Aegeria), with nearly a dozen species of smaller size. A third genus, Sciapteron, is doubtfully native with us. They are much prized by collectors on account of the rarity of the Insects and their great difference in appearance from our other native Lepidoptera.
Fam. 14. Tinaegeriidae. This is one of the least known of the families of Lepidoptera, and has only recently been distinguished from Sesiidae. It is entirely exotic, and our knowledge of it is principally due to Lord Walsingham.[[270]] Nothing is known as to the life-histories, except that it has been stated by Stainton that a larva feeds in webs on shoots of a shrub of the genus Clerodendron. The family is widely distributed, but its metropolis will probably prove to be the tropics of Africa. It is of considerable interest as showing that the Sesiidae really belong to the Tineid series of moths. The species we figure (Fig. 193) has a character otherwise peculiar to Sesiidae in the wings being inserted on the thorax remote from the head—a feature we do not find in the Tineidae proper; while on the other hand it has the long wing-fringes, and the shape of the wings that are characteristic of Tineidae. It is worth mentioning that though these Insects are of excessive rarity and very peculiar, there exists in the Solomon Islands[[271]] a species distinct from, though at first sight excessively similar to, the S. African one we figure.
Fam. 15. Syntomidae.—This family has usually been associated with the Zygaenidae. It includes a large number of moths having, as a rule, in external appearance little to distinguish them from the family named. Many of them are of gaudy colours, and probably of diurnal, but somewhat sedentary, habits. The wings are less ample than usual, the hind pair frequently very small, so that the Insects have somewhat the proportions of Hymenoptera. In some cases the resemblance is made more remarkable by the fact that the wings are transparent and bare of scales, or have scales only at the margins, so as to be like the wings of Hymenoptera. Not less remarkable is the fact that these Insects use the body itself for the purposes of adornment or display; thus adopting a system prevalent in the Hymenoptera, rather than that of their own Order, where the rule is that the wings are more ornamented than the body. In many cases the shape of the body is so very different from the normal that the disposition of the organs of life in the interior of the body must be materially affected. In some genera, such as Andrenimorpha, the form, colour and attitude of the body and some of the limbs are plainly similar to Hymenoptera. These Insects have a highly-developed frenulum, retinaculum, and proboscis; bipectinate antennae in the male, a complex organ at the base of the abdomen on each side, and are in fact highly-developed forms, except perhaps as regards the structures in connexion with flight.
Unfortunately little or nothing is known as to the habits and metamorphoses of these extraordinary creatures, but it is no doubt to them Seitz referred in saying, "How far one may be deceived by appearances of a mimetic nature can only be comprehended by visiting the tropics; in this part of the world [Europe] one is prepared by knowledge gained from books for the appearance Sesia presents. Had one no knowledge of this sort as to Sesiidae he would actually in the field [in Brazil] overlook dozens of these little creatures without being aware of his deception. The surprise at finding a quite different being in the net from what one believes he has caught occurs daily in Brazil, so rich in Lepidoptera."[[272]] The same intelligent observer says[[273]] that a species of Macrocneme was observed by him to be exactly like one of the blue wasps of the genus Pepsis.